the #1 rule

What is the #1 rule that to you makes a classroom work? why?
I believe the number 1 rule is discipline although i hate it. I am not a person of rules and regulations, i like to give away little loopholes on my rules or beliefs however, discipline is truly the number 1 thing that makes a system works. I used to believe that joy and happiness would bring much greater obedience to people, but after reading Machiavelli's "the Prince" my views toward discipline and fear have totally changed. Now, i believe the greatest way to ensure people listen to you is through fear, as of discipline, its just like fear. By having fear and respect in the hearts of people prevents them from doing against the norm. They would follow orders given from the teachers, be aware of the deadlines and respect the teacher. I learn this lesson hands on in the classroom of Ms. Brown.
Ms. Brown's classroom wasn't fun, but she ensured us of discipline and knowledge. I learned a great deal from her since she was quite the fearful looking person i have ever met. Whenever she do something in class or say something, no one, and i mean nothing would dare disturb her at all. A look from her would alarm us to behave. That, is respect for her way of dealing and fear of what she might do. The methods of Ms. brown wouldn't work for everyone, but i believe through her example and "The Prince" i have understand the true meaning and power of discipline and fear.